In counter-current types of centrifugal separators for separation of liquid and solid particles from a gaseous medium a negative or sub pressure is created in the separation chamber of the housing. This sub pressure causes the gas to be sucked in through the gas inlet that opens into the separation chamber of the separator housing. The liquid separated in the rotor is thrown out onto the inner wall of the housing and flows by gravity downwardly towards a liquid outlet in the bottom of the separator housing. The liquid is then led to an external container through a hose or pipe conduit. However, the sub pressure in the separation chamber also causes air to flow into the separation chamber through the liquid outlet conduit. This air flow prevents the separated liquid from flowing out through the hose, resulting in a back-flow which gradually fills the separation chamber with liquid until it eventually reaches the rotor and is thrown around. This causes the rotor to be overloaded. In order to prevent this from happening the inner end of the outlet hose has to be immersed below a liquid surface in the separation chamber, such that no air could be sucked in through the outlet hose. However, such a liquid surface is not always available. The hose configuration is also very delicate. If the hose is laid out such that liquid somewhere has to flow upwardly, a further liquid trap is formed which then will prevent the outflow of liquid from the separator. Also, the level of the liquid surfaces present in the separation chamber varies, e.g. when tanks are emptied, whereby the end of the hose suddenly could be located above the liquid surface and prevent flowing out of the liquid.